Hob-grinding machine



J. EDGAR HOB GRINDING CHINE Filed Juni 28, 1915 er: Q?! ,muli i wmf" "wll E .,1 l g [t mmmr F'IC. .l

J. EDGAR HOB @BINDING MACHINE Nov. l0, "1931.v

Urginal Filed June 28, 1916 5 Sheets-Sheet 2 lll IIIIIII I|...|| I I i I I I I l l I l l I I l 1 15.1. a. w N s r V 1L +V? I bq vIIIH H.|I'1 1.I| I||r.|ll 'fr A\ IIIUI IIIHJHHIWIHI .i 1 i I E QN l U N .w QN m M l ,u R m .u F f .w Q Q T w QM m www uw M.

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J. EDGAR 30B GRINDI NGMAGHINE Nonno, 1931.

Origxxal Filed June 28, 1915 .5 Sheets-Sheet 25 J. EDGAR HOB 'GRINDI NG MACHINE Filed June 28, 1916 Original Filed June 28, 1916 Nov. 1o, i931.

5 Sheets-Sheet 4 mmm F-ICJJ J. EDGAR t 1,561,064

Nov. 10, 1931. HOB GRINDING MACHINE Original Filed June 28, 1916 5 Sheets-Sheet 5 F'ICJ Passed Nev. 10,1925.

UNITED STATES .Toms or Bomann, more, assrcnon, Bv 11m-sm: assronnnnrs, To.

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PATENT OFFICE.

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wenn nea Jue as. ma. semi n. mesas.

To a whom it'jmay Be it known that I Joint Encan, a sub ject" of the King of Ireland, residing atRockford, in the county 5 of Winnebago and' State of Illinois, have .inventcdfcertain new and-useful Improvements in Hob-Grinding Machines, of which the following isl a specification. This invention relates to the manufacture l ofhobs used in generating spur and iral ar wheels. After the rtlally-comp eted obs have been harden f fit; is n to grind the teeth of thehobs to give em correct form and dimensions.

l The object of this-invention is to produce :1 machine by means of` which the teeth of :1- hob may be quickly. and accurately ground to form and s1ze. y l

A hob has one ormore spiral series of relieved cutting teeth, the -cutting faces of the teeth being delined by gashes which may be either strai ht '(i. e., arallel. with the axis of the h or xpi L In". order that the hob shall have re atively lo circumferential length of the teet is 4made asnsgreat as possible; which means that the g' es are relatively narrow-much narlower, proportionate in the case-.of ata or instance. Hauseof the length of e teeth, there is considerable difference 1 between the height of aY tooth at its front end, audits height vat its rear end, which fact necessitates a relatively lo relieving stroke and an abrupt return stro e.` Morcover,1 because 4of the'narrowne'ss ofthe gashes it is impracticable 'togrind the two opposite sides of a tooth space at the Asame time. Before one such tooth space the grinding wheel would engage the next tooth Spwe L In order to`av'o`d'rotat' the element at an objeiionablynigh an to prevent excessive wear on .the grinding element, it is `de sirable.tnusean abrasive wheel 4of relatively large diameter; -and in order to obtain clearance between the wheel and each succeeding tooth, it'4 is desirable to mount thewheel so that its periphery may be employed in .i

The machine herein disclosed is specially ada ted to fulfil .the requirements peculiar to t e grinding of hobs,. straight-gashed as 4.G'rreat Britain and' life, the

well as spiral-Vgashed, and to produce ac curate work at a relatively fast rale and vention. Fig. 1l is a fragmental sectionalV view of the tail stock of the machine. Fig. A

1" illustrates the position ofthe rinding wheel with relation to the hob. ig. 2 isl a sectional view of the connection between the hob slide and the feed-screw for moving said slide, the view bein taken in the plane of dotted line 2-2 of fragmental side elevation of the machine. Fig. 4 is a section taken in the plane of dotted line 4 of Fig. 1. Fi 5 is a section taken in the plane of dotto 1-. .Fig. 5* is a view of a clamp for the wheel-ca ing head. Fig. 6 is4 a section on dotted 'ne 6 of Fig. 1. Fig. 7 is a horizontal central sectional view of the hobsupporting means. Fig. 8 is a view look` ing from the left-handend of Fig. 3Q Fig. 9 ls-a sectional view of the means for rotating the hob. Fig. 10 is a view of the means for indexing a plural-thread hob. Fig. 11

lis a section on dotted line 11' of 4. 12 is a section on dotted line 12 of ig.

4. Fig. 13 is a section on dotted line-13 of Fig. 14.' Fig. 14 is a section on dotted line l1 4 ofFig. 1. Fig. 15 is a section o n dotted line 15 of Fig. 5. Figs. 16 and 17 are' views of an attachment for dressing the wheel. Fig. 18 is a to plan view the grinding wheel, the rotation and movement of translation of the hob bein so proportioned to each other that one si e of the thread (or, more accurately speaking,

ig. 5. Fig. 3 is s line 5 of Fig.

6 position and adjustedwith relation to the grinding wheel so that the 'latter' shall be able to remove more material. The hob is' then rotated and fed the wheel as before. Thesefo l tions are repeated 4'until oneride of eth1-cad of the h ob has been completely ground The head extending lugs 32 (Figs. 2 and 5). A bearthat carries the ding wheel is then reversed so-as to in position to ind the other side of the thread of the lglob. 'The hob is then :fed past the grin the thread has roperly: -v A slide 1, I lponwhlicli thehobis spported, is mountedupon two ides 2 -a`nd 3 (Fig. 5) formed u on the of the machine. Upon 'th'es "de 1 is a head-stock 4 and a tail-stock 5, the'latter he adjustable toward and away from thehea -stock upon a guide 6. Thetail-stck is'secured to the slide 1 'in adjusted position by means of a bolt 7 12 extending 4through the tallstock, t eiea 'oisaid boltlyling within a T-slot 8 in the slide. A spin o 9 (Figs. 1, 3 and 7) is rotatably supported in the headstock 4 andA is held against longitudlnal movement in said head-Stmk by means of a flange 10 anda collar' y11.` 'I he spindle 9 is made tubular to Vpermit of inserting and removinthe su rt or arbor 12 that carries the ho The a r 12 has a tapered rtion adapted to be driven' into a eo l n glytnpered socket in the end of the spmdle 9. The spindle being tubular, as shown in Figs. 7 and 9, a rod may be into the other end of the' spindle for the purpose of drivin outthe arbor '12 when www' The ho is secured upon the arbor between' -an annlar shoulder 13 and a nut 14, and is further held against rotation with relation to the arbor by means of a key 15. The end -of the arbor opposite to the tapered end is provided with a center 16 av to be sup orted by a sleeve .17 carried by the stoc 5. Said sleeve is held notation by means of akey 18 and is arranged to be moved into and out of o rative relation to the center 16 bymeans o a screw 19 having an o ratin hand wheel 20, Clamp mem-` bers 17 (Fig. 1*) anda screw' 17h provide means for securely locking 4the sleeve 17 against movement. l

The means for rotating the spindle 9 comprises a sleeve 2 1 a9) rotatably mounted in bearings22 anl23 inthe supporting framework ofthe machine The spindle 9 is slidable longitudinally o f the sleeve 21, but is caused to rotate with the sleeve b means of a spline 24 (Fi 9) connec to the sleeve and lying witiin a keyway 25 Ain the the grinding wheel.

V34 to cause the lugs and .wheel the desired numberrv of times until t e last mentioned 'side of s indue. By meins te be later described, the

eeve 21 is adjustably connected to a wheel 26 that meshes with a pinion 27 1) ixclieodn the drigshalft 28. Og sa'd sul issec astep p'ey29. ai `p is driven roma reversible countershaft (not shown) or other suitable source of wer.

T he means-for f "'the sli e 1 com-V prises a f eedscrew 30( igs. 4 and 5 sup` rted in a '31 in the machine me. igid with the Slide 1 are two downwardly ing 33 lies between these lugaand has anges i ring to travel together. Rotatablly mounted in the bearing 33 is a nut 35,V Sai nut being -held against endwiselnovement with relation to the bearing 33 by means of a shoulder'36 and a nut 'T37'. The nut 35 vis threaded upon a mit 38 on the feed screw 30.l The nut 38 'is pie vented from rotating with relation to the bearilig33 by means of an arm 39 which i's rigid withsaid nut7 said' arm havin an opening through which va pin 40 is sli able (see Fig. 4), said pin being fixed in the bearing 33 and extending longitudinally of the feed screw 30. When the feed screw 30 is rotated, the nut 38 will be caused to move longitudinali of said feed screw, the nut 38 carrying 'v it the nut 35, thebearing 33 and the lugs 32, and thus imparting movement to the slide 1.

In order that .the slide 1 shall be adjustablel withrelation to the. nut 38 I provide a shaft 41 rotatably supported in the slide' 1 vand having u n its lower end spiral gear teethv42 `mes with similar teethv 43 formed-upon the nut 35. The upper end of Y the shaft 41 is squared to'recelve a crank. Fixed to the shaft 41 is a micrometer dial 44 arranged to coact with a zero.' mark on the adjacent portion of the slide. After` the wheel "B has-made a cut and the slide 1 has been returned, the slide may be adjusted by means of the shaft 41 to permit the ding wheel B tomakeanother cuton idnsame side of thethread of the hob.

The feed screw 30 is arranged to be rotated by power means for advancing the hob` withre'lation to bhe, grinding wheel and is also arranged to be rotatedby manually actuated means for the purpose of returning the slide 1 to initial position; said manually actuated-means comprises a; shaft 45 (Figs. 4

1, 3' and 4), said shaft being connected t0 the feed screw 30 byv means of spiral gears 46 and the outer end of said shaft being Y squared to receive a crank.

clutch member are caused to rotate together by means ofa key 50 (Fig. 11) The clutch `ber 49 has been member 49 is arranged to be slid-longitudinally of the feed screw 30 by means of a fork 51 engaging said clutch member and fixed upon a rock shaft 52. U n the outer end of the rock shaft 52 is xed a hand crank 53 (Fig. 3 After the clutch memisengaged from the clutch shaft 47, the shaft 45 ma be rotated to adjust the slide 1 to place t e hob in approximately o erative relation to the grinding wheel. ixed to the clutch shaft 47 is a change-gear 54 (Figs. 4 and 8) meshing with a. change-gear 55; the latter gear is rigid with'a chan e-gearthat meshes with a change-gear 56; t e change-gear 56 is rigid wlth a gear 57 that meshes with a gear 58 which is rigid with the ear 26; the latter, it

will be remembered, mes es with a pinion 27 on the drive shaft 28.

, A hob may have one or a plurality of threads. After one thread of a multiplethread hob has been ground, it is necessary to turn the hob to bring another thread into position to be Ground. For this purpose the spindle 9 is adgustably connected to the gear wheel 26. Ri d with the sleeve 21 is a flange or disk 59.' ring 60 is adjustably secured to the disk 59 by means of bolts 6l extendin through the disk 59 and having heads t at lie within circular under-eut slots 62 in the ring 60. The ring 60 is adjust-V ably secured to the gear-wheel 26 by similar clamp bolts 63.* For setting the ring with relation to the gear-wheel 26 there is provided a spring-pressed index pin 64 carried by the gear-wheel 26 Vand arranged to enter any one of a number of opeuin s 65 in the ring 60." When one thread o a doublethread hob has been ground, the clamp bolts 63 are loosened, the index pin A61- drawn back and the ring-60 turned through onehalf of a revolution, thus bringing an openin 65 into register with the index in 64, -Whlch latter is then 4 ermittd to s1 rlng into said opening. In t e case of a triplevthread hob the operator would turn the rin 60 with relation 'to the gear wheel 26 througA one-third of a revolution, thus bringing anv opening 65'into register with the index pin 64. For thus turning the ring 60, a bar (not shown) would be inserted in openings 21" fius . ad3ustab1y connectedtogether as ((Fig. 9) in a collar on the sleevf4 21. Any

esired number or arrangement of openings 65 may be provided to take care of hoIbs n order thatthe spindle 9 may be ad'usted for hobs having a number of th'rea s not provided for by the spacii of the opnings 65, the disk 59 and e. ring 60 are ereinbefore stated. A graduated ring 66 is rotatably mounted upon the periphery of the disk 59 and is secured thereto in adjusted position by means of a. clamp bolt 67. Onh1 the ring 60 is a Vernier 68. Normally the zero line on the Iring 66 is o posite the zero line of the Vernier 68. A er one thread of a hob having such special number of threads has been ground, the hob is turned to bring the next thread into position to be acted upon by the wheel B by loosening the clamp bolt 61 and turning the disk 59 with reference to the Vernier 68 through an arc of the necessary length. The clamp bolts 61 are then tightened, the bolt 67 slackened, the ring 66 returned to zero position and the bolt 67 again tightened. )Vixen the next thread is to be ground, the flange 59'is again turned. with reference to .the Vernier 68 ifzhrough 'the Isame angular distance as beore. v Y

The adjustable connection between 4 the flange 59 and the ring 60 affords means for conveniently setting the hob with relation to the relieving cam 71 so that as the hob rotates the grinding wheel shall be moved outwardly in time to begin operation on each succeeding tooth.

The grinding wheel B is carried by a slide 69 (Figs. l and 5) which is re'ciprocable at right angles to the direction of movement of the slide 1. As shown in Fig. 5, the teeth of the hob A are relieved with a uniform clearance. wheel B, the slide 69 is moved toward the slide 1 to maintain the wheel in proper relation to the tooth. As soon as the tooth hasy passed the wheel the slide 69 is given a quick outward movement to place the wheel B in osition to grind the next succeeding tootii. The means for thus reciprocating the s1ide`69 compriscsa shaft 7 0 (Figs. 1, and 5) carrying a cam 71 ar- As a. tooth revolves past the ranged to operate a ainst a block 72 upon the slide 69. As slown in Fig. 14, the shaft 70 is ymade in two sections connected by the one-way clutch 73 shown in Fig. 13, in order that the cam 71 shall ,not interfere with reverse movement of the rest oi the 1nachinewhen it is desirable to turn the drive shaft 28 backward in adjusting the relation of the hob to the grinding wheel. The shaft 70'is driven from the drive shaft 28 through change gears 74, 75 and V76 (Fig. 8). i

The slide 69 is moved away from thehob by means of a coiled compression spring 77 (Fig. 5) which bears at one end against a stationary post 78 and is adjustably connected at its other end to a lug79 on the slide 69. A rod 80 fixed to the post 78A las movement of the slide 69. When the machine is running the slide 82 is stationary with relation to the slide 69, but means is provided whereby the slide 82 may be moved toward and away fromthe hob when the machine is being adj usted. Referring to Fig. 5: A. bar 83 is fixed to a lug 84 on` the slide 69. On the bar 83 is slidably and rotatably mounted an adjustin screw 85 having holes 85Vto receive an imp ement.for turning the screw. The screw 85 is slidably and rotatably supported in a guide 86 on the slide 69.` `*A coiled compression Yspring 87 surrounding the bar 83 bears at one end against the lug 84 and at its other end against a portion of the screw 85. The s ring 87 is restrained by a hand lever 88 ig. 1) which is pivoted to the outerend of the bar 83, said hand lever having a cam rtion 89 that bears against a washer Whic in turn lies in contact with the screw 85. A detent 88 yieldingly locks the handle 88 against movement.

It will be seen that'I have rovided three mutually independent means orproducting movement of the slide toward and awayv 4 from the hob, namely, the cam 71 and the spring 77, the screw 85, and the hand lever 88 and its connections.

The slide 82 is fixed to the screw 85 by the* means shown in Figs. 5 and 6. 90 is a nut rigidly secured to the slide 82 and engaging the screw 85. In order that the nut 90 may be tightly clamped to the screw 85, said nut is s llt at one side (as at 91) and is arranged to e contracted into clamping engagement with the screw by means of a screw 92.

The grinding-wheel spindle is carried by a frame 93 (Fig. 15) provided with trunnions 94 which are mounted for oscillation in a bearing 95 on the slide 82 and in a bush-- ing 96 carried by a portion 97 of the slide 82. It will be observed that the bearing 95 and portion 97 of the slide to ether constitute a tool post in which the too -carrying frame 93 is pivoted upon an axis a,- (Figs. 1" and 15) intersecting the axis b of the hobiat a right angle. 'When grinding the bob the point of intersection c of the pitch line d of the hob and the line of contact of the hob and the inding wheel is in the axis a of the trunnions 94. The frame 93 is arranged to be held against swinging movement by.l

means of a screw 98 engagmg a'threaded opening 99 is said frameand adapted to extend through either of two diametricall'y opposite curved slots 100 in the slide portion 97. When dressing a grindin w-hee'l that is to be used in indmg the teet of 4a. spirally shed hob, t e frame 93 should be secured 1n the horizontal lane of' the spindle 9, and for this pur ose lllprovide a positioning pinY 101 adapte to be inserted into either one of two openings 102 provided at diametrically opposite points in the portion 97. The

responding to the angle of the thread of the hob, I provide a protractor ring 104 (F1 s. 1, 5 and 15) `rotatably mounted upon elle bushing 96 and arranged to be clampedto the portion 97 by means of bolts 105 extend; ing 4through the portion 97 and having heads 'lying in an annular T-slot 106 in t e protractor rin `At diametrically o posite points on t e `protractor ring are `iormed notches 107 to receive a spring-pressed de tent' in 108 carried by theframe 93. For

with rawing the pin A108 from engagement with a notch 107, there is provided a pinion 109 arranged to engage'rack teeth formed on the pin 108. The upper end of the piniloll 109 is adapted to be engaged by a key The protractor ring 104 is provided with graduations as shown in Fig. 1, and the portion 97is'provided with a co-operating `zero mark.

The grinding-wheel spindle is carried by a power head 111 which is mounted in a clamp on the frame 93. The construction of this clamp will be apparent from Fig. 5". T'lhe jaw 112 of the clamp is relatively stationary, while the jaw 113 is arranged to be drawn toward the jaw 112 b means of a bolt 114 and nut 115 so as to c amp the head 111 rigidly, tothe frame 93.` The clamp jaw 113 is loosely secured to the frame 93' by means of two screws 116 (Fig. 15). After the nut .115 has been loosened, the head 111 may be slid back and forth with .relation to the frame 93 by operating nuts 117 on a screw stud 118 fixed to the frame 93, said nuts lying at opposite sides of a lug 119 on the head 1 11.

The grinding wheel B isremovably secured in any usual or'suitable way to a spin- Vdle 120 (Fig. 15), the axis Vof which intel'- sects Vthe axis of-the frame 93. Said spindle has a tapered portion. which lies within a correspondingly-tapered bushing- 121 in the head 111, the spindle being urged forward against said bushing by means of fa coiled 'spring 122. Fixed to the spindle 120 is a gear wheel 123 that meshes with a ear wheel 124 on -a shaft 125 arranged 'para lel to the spindle and carried by the head 111. Rigid with the shaft 125 is a bevel gear wheel 126 that meshes Vwith crown gear` teethv formed upon one side-of a flanged driving pulley 127, said pulley being rotatably mounted upon a stu 128 fixed to the head 111i The pulley 127 receives a belt 129 extending from y a counter-shaft or other suitable source of ing the several adjustments may be varied,

the o'peration of grinding a single-thread hob may be described,iii` general, as follows: The handlel 88 (Fig. 1) is operated to allow the spring 87 (Fig. 5) to more the slide 82 outwardly. The frame 93 is adjusted, with thc aid of the protractor ring 104, to the 1proper inclination with reference to the ang e of the thread of the hob (sce Fig. 3), the frame 93 being secured in adjusted position by means of the screw 98. The tail-stock 5 isslid away from the headstock 4. The arbor 12 is inserted int-o the tapered end of the spindle 9. The hob is placed on said arbor-and secured thereto means of the nut 14. The tail-stock is sid up to place-the end of the sleeve 17 against the center 16. The nut on the bolt 7 is tightened up to clampfthe tail-stock in place." The hand-knob 20 is turned to press the sleeve 17 against the center 16, and the sleeve is locked in adjusted position by means of the'clamp 17. The clu'tch 49 being inthe thrown-.out position, the shaft 45 is rotated manually until the side of the forward end of the thread is near the working portion of the grinding wheel B, after which the clutch 49 is thrown in. handle 88 is then turned to advance the wheel B toward the hob. The flange 59 is then adjusted with relation to the ring 60 until the hob is in proper relation to the cam 71. The machine is then set in operation, whereby the wheel Bis rapidly rotated, the slide 1 slowly advanced, and the spindle 9 slowly rotated. By means of the shaft 41 the operator accelerates the feed movenient of the slide 1 until the grinding wheel is making a proper cut. After the hob has been fed past the grinding wheel B the ma'- chine is stopped, said wheel is withdrawn by p operating the handle 88, and the slide 1 is returned to initial position by reversing the drive `for the pulley 29. After the slide has been returned to initial sition, the machine is stopped, the whee B is returned-to working osition by means of the hand-lever 88, and t e machine again set in operation to feed the hob past the grinding wheel. The operator turns the shaft 41 so as to advance the slide 1 suliciently to enable the wheel B .to make a second cut of proper cam de tli. i

lifter one side of the thread has been completely ground, the machine is stopped, the clutch 49 thrown out, the wheel B retracted by 'means of the l'ever 88, the slide 1 returned by means of the shaft 45, and the clutch 49V thrown in. VThe screw 98 (Fig. 15) is withdrawn; the detent pin! 108 is removed frpnr lshe notch 107 with which it is in engagement; the frame 493 is swung tlirouglvan `arc o 180 degrees until the datent pin 108 springs intol the other notch 107: the screwA 98 is inserted into the other slot 1.00 and The into the hole 99 and tightened to secure the frame 93 rigidly in place. The belt 129 is then removed from the pulley 127 and twisted and replaced. The wheel B is then moved forward into grinding position. The slide 1 is then adjusted to move the hob longitudinally, a distance approximately one half the circular pitch of the hob so as to bring the ungroiind side of the thread into approximate position to be ground. The machine is started up and the shaft 41 is turned until the Wheel is making a proper cut. After the second side of the thread has been made smooth, the operator employs at intervals a suitable uge in order to ascertain when the m0 has beenl completely ground. The form of gauge herein shown comprises a gauge member130 (Figs. 1 and 5) mounted for sliding movement toward and away from theV hob in a carrier 131. said carrier being slidable longitudinallyT of the hob on a guide bar 132. The bar 132 is removably and stationarily supported upon two posts 133 on the slide 1. The gauging ii of `course, done when the machine is i e.

In grinding a multiple-thread hob' the spindle 9 is indexed or lturned with relation to the gear wheel 26 after each thread has been completley ground. A suitable gauge (not shown) would be applied by the operator to determine when the grinding of a thread has been completed.

Suitable modications are made in the change-gear train 54, 55, 56' in accordance with changes in the number of threads of the hob.

As shown, the machine is arranged to grind a right-hand hob. To operate upon a left-hand hob an additional change gear (not shown) would be provided in the gear train 54, 55, 56 so as to reverse the direction of feedinovement of the slide 1.

Chan in the gear train 74, and 76 are ma e as required bythe number of flutes or gashes in the hob to be ground, and when 'to one having spiral tintes-or vice versa.

Variations in the amount of relief of the` teeth of the hobs o rated upon are taken care of by ch in the shape :if the 71. To dress the grinding wheelI provide means comprising a bracket 134 (Fig. 17) having a base 135 adapted to be seatedrion the guide 6. To the base 135 is secu a notched h ig 136 adn. *Bd 170 L pitionlng pm 137 fix to the sli e 69, whereby the bracket134 may be properly located opposite the grinding wheel. The bracket'134 is ad1ustble upon the base'135 toward and away from the grinding wheel by means of a screwthreaded rod 138 secured to saidbracket and having a mit 139 thereon. Saul mit rests sha'pd periphery of the' in a recess in the base 135 and is held b the walls of said recess against lon tu al movement. An arm 140 is provi ed at its lower end with a rod 141 which extends slidably through a ball 142. Said ball is `rotatably mounted in a socket 143 in the lower portion of the bracket 134. The lower end of the rod 141 is provided with a int 144 that rests in a sockel 145 in the ower part of thebracket 134. The upper rtion of thearm 140 is provided with a kni e edge 146 arranged to be moved along the edgrpf a templet 147. The outline of the wor g portion of the templet 147 corres nds to the outline to be imparted to the si es of the teeth of the hob. The templet 147 is arranged to be secured to the upper portion of the bracket 134 b means of screws 148 and washers 149 over ing said templet. As indicated by full an dotted lines in Fig. 18, the tem let may be secured to the bracket in either ci' two positions so that the wheel may be dressed when the frame 93 is in either of its two horizontal positions. At the upper end of the arm 140 is a handle portion 150. A dressing tool 151 havinga point of suiciently hard material is located on the arm 140 in the horizontal plane of the axis of the wheel B andis secured to the arm 140 by means of nuts 152. For convenience in locating the point of the dressing tool in the line containing the center of the ball 142 and the knife edge 146, I rovide flattened pins 153 and 154 above an A below the dresaing tool, against which pins a straight edge may be placed to serve as a guide in positioning the dressing tool. The radius of the socket 145 is suchthat as the arm 140 is oscillated upon the center of the ball 14,2 and moved along the edge of the tem late 147,. the arm will be moved up and own suiliciently-so that the intof the dressing tool shall trace, in a orizontal glane, the contour of the surface to be groun upon the teeth of the hobs. The hob illustrated in Fig. 1 has ystraight flutes or gashes, that is to say the gashes are parallel to the axis of the hob. Some hobs are provided with ral gashes which are normal to the As' hereinbefore stated.- when' dressing a wheelthat is'to be used for iuding the teeth of a spirallygashed ho J the frame 93 is secured in horizontal position. When dressing a wheel to be used for grinding the teeth of a straightgashed hob, as herein shown, the frame 93 is secured in a positibn inclined `to the sama degree as when While -the wheel is being m. it may be rotated in a reverse direction, if desired, the belt 129 be' ari-an recco f l A decrease in e diameter of the w due to wear and dressing, 'is adjusted for by advancing the slide V82 with relation .to the slide 69 by turning the screw 85, and by re acero 1ti'acting17 the head 111 by adjustmg` the nuts While I have described the present einbodiment of the invention in considerabledetail, it will be understood that the invention is not limited to the construction herein shown, except as indicated by claims. V

I claim as my invention 1. A hob-grindingl .machine having, in combination, a rin ,'ng wheel, anrotatabl mounted spin e for supporting a ho means for causing ative movement between the wheel and the hob longitudinally of the hoba drive wheel concentric with the s indle forrotating the saine, and adusta le means connectip the spindle and 'rive wheel to rmit of ative rotation between the saine including an intermediate member, said intermediate member being adjustable with res to both spindle and ,drivin wheel an rigidly secured to each in the a justed position.

2. A hob-grinding machine having, in combination, a support for a hob means for rota said su port around the axis of said ho and sli 'ng it along the axis synchronously, a tool adapted to slide alon an axis perpendicular to the axis of said hob, and also rotatable around its axis of slidiiig, means. for clamping said tool in adjusted :nular position and means for slidingsaid 3. A hob-grinding machine having, in combination, a 'grinding wheel, a slide, means on the slide for rotatably supporting a hob with its axis extending in the direction of movement of the slide, a feed screw for moving the slide, a nut on said screw, and manually adjustable means connecting said nut to the slide for movement of the slide Vith relation to the nut longitudinally of the screw.

4. 'A hob-grinding machine having, in combination, a slide, means on the slide for rotatably su portinga hob with its axis exthe appended tending in't e direction of movement of the slide, a feed screw for moving the slide, a nut on the feed" screw, a nut secured upon the mentioned. nut, mean's rotatably connecting the second nut to the slide, and means for rotating thesecond, nut. p

5. A hob-grindi machine having, in combination, a grin 'ng wheel, a rotatably mounted spindle for supporting a hob, means for causing relative movement between the wheel and the hob longitudinallyof the hob, a wheel for rotating the s indle, and adjustable means connecting t e spindle and second mentioned wheel tu 't of relative rotation between the spin e and said second mentioned wheel.

6.' A hob-grinding machine hav in combination, a hob-supporting spind e, a ring to said spindle to'notate thereiis with, a drive wheel concentric with the spindle and rin and means for adjustably connecting sait ring and wheel for relative rotation.

7 A hob grinding machine having, in combination, means for rotatably supporting a hob a slide, a grindin wheel carried bythe slide, andthree mutua ly inde endcnt means for producing movement of tie slide toward and away from the hob.

8. A hob-grinding machine having, in combination, means for rotatably supporting a hob, a slide recipioeable in a direction at right angles to the axis ofthe hob, a grinding wheel mounted on the slide, a rotary cam for moving the slide inone direction. and a spring for moving the slide in the opposite direction.

9. A hob-grinding machine having, in combination, means for rotatably supporting the hob, a frame pivoted upon an axis intersectin the axis of the hob, means for securing said frame in adjusted position, and

- a grinding wheel carried by said frame.

10. A hob-grinding machine having, in combination, means for rotatably supporting a hob, a frame pivoted to swing upon an axis intersecting the axis of the hob, means for securing said frame in diametrically opposite positions and a grinding wheel carried by the frame. l

1l. A hob-grinding machine having, in combination, means for rotatabl supporting a hob, a slide movable toward and away from the hob, a frame pivotcd to the slide to swin upon an axis intersecting the axis of the lob, means for securing said frame against swinging movement,` a grinding wheel carried by the frame` and means for moving the slide toward and away from the hob.

l2. A vhob-grinding machine having, in combination, means for rotatably'siupporting a hob, a frame pivoted to swing upon an axis intersecting the axis of the hob, means for securing said frame in diametrically opposite positions, a head adjustably supported by the trame, and a grinding wheel carriedby the head.

-13. A hob-grinding machine having, in combination, means for rotatably lsupporting a hob, a frame-pivoted to swing upon an axis intersecting the axis of the hob, means` for securing said frame against swinging movement, a head mounted on the vframe for movement on an axis intersecting the axis of the frame-,aand a grinding wheel carried by the headh v `14. A hob-grinding machine having, in combination. a grinding Wheel, a slide, means on the slide for rotatably supporting a hob with its axis extending in the direction off movement of 'the slide, means for rotating the hoba feed screw, a nut on the feed screw, said feed screw and nut bcing arranged to move the slide when the feed screw is rotated, power means for rotatin the feed screw, a clutch connecting the fee screw to said driving-means, and manual means for .rotating the feed screw.

15. A hob grinding machine having, in combination, means for rotatably supporting a hoh. a slide mounted for movement toward and away from the hob', a grinding wheel carried by the slide, relieving means adapted to reciprocate the slide toward and away from the hob, adjustment means indeendent of said relieving means for moving the slide, and a third means for moving the slide to withdraw the` grinding wheel clear of the hobwithout yinterfering with the o eration or adjustment of said relieving or a justment means.

16. A hob grinding machine having, in combination, means for supporting n. hob and moving the teeth of the hob' through helical paths, a grinding wheel slidable toward and away from the axis of the hob, means for reciprocating said grinding wheel to relieve the teeth of the hob, and connections for driving said reciprocatingmeans from the means for moving the hob, at any desired speed ratio. 4

17. A hob-grinding machine having, in combination, a hob-carrying spindle adapted to simultaneously rotate and slide axially, a

ltool slidable on an axis intersecting `the axis .of said spindle, and means operative to reciprocate said tool' upon rotation of said spindle in one direction, said means being inoperative when said spindle is lrotated in the opposite direction.

18. A hob-grinding machine having, in combination, a. hob-carrying spindle, means for rotating said spindle and simultaneously sliding it axially to carry the teeth on said hob in helical paths, a tool slidable at right angles to the axis of said spindle, a countershaft parallel to said spindle, a camon said coun'tershaft adapted to reciprocate said slidable tool, and an operative connection between said spindle and said eountershaft. 19. A hob-grinding machine having, in combination, two parallel spindles, change gears determining the relative speed of sai two spindles. one, of Vsaidspindles being adapted to slide axiallyfas well as rotate, means for axially moving said lspindle at a constant pitch, a tool adaptedl to reciprocate in a line perpendicular to the axis of sai slidable spindle, and 'a cam on the other spindleoperativelyconnected to said tool to reciprocate the' same. n

20. A hob-grinding mac,4 ine having, in combination, a hob-earryi 4 spindle adapted to rotate and move axi yat a constant pitch, a conntershaft parallel to said spindle, means for driving said countershaft, acam mounted for rotation on the same axis as said counter-shaft,- a connection between said cam and said countershaft adapted to transmit rotation in one direction only, a tool slidable on a line at an angle to the axis of said spindle and an operative connection between said cam and said tool.

21. A hob-grinding machine havin in combination, means for supporting an rotating a hob, a grinding wheel, a rotatable shaft carrying said grinding wheel, a power tating a hob, agrinding-wheel, a rotatable shaft carrying. said grin ing wheel, a power head carrying said shaft, said head being of greater radial dimensions than said wheel, and said shaft lying at an oblique angle with respect to the axis of said lio'b and projecting from said head to provide clearance between said head and said hob and hob-supporting means. Y

23. A grinding machine having, in combination, a work carriage, a power transmission for rotating the work on said carriage, manual adjustment means interpolatedl in said power transmission for synchronizing the same with other parts of the machine, a power transmission for sliding` said carriage, and manual adjustment means interpolated in said last mentioned power transmission.

24. A grinding machine having, in. combination, a work carriage, a power transmission to said carriage including a nut and a cooperating feed screw, and manual adjustment means interpolated in said transmission for manually producing independent longitudinal adjustment of said carriage.

252 A grinding machine having, in combination, a carriage, a connection transmitting powerthiough a plurality of intermediate elements including a feed screw and cooperating nut' for sliding said carriage, and means operating on one of said intermediate elemenvts for manually producin independent longitudinal adjustment of sai carriage.,

26. A grinding machine having, in combination, a carriage, Va feed screw and cooperating nut, a power transmission for rotating one of said two last mentioned elements, vand a mechanical connection between the other element and said carriage normally constraining them to reciprocate in unison but adjustable to produce limited longitudi- .ial displacement of said carriage independent ofvand superposed upon the-movement produced ,by said power transmission.

machine having, in

27. A hob grindin r rotatably Ysupportcombination, means.l

ing a hob, a frame pivoted to swing-upon an axis intersecting thc axis of the hob, means -for securing said frame against swinging movement, a shaft mounted on the frame for rotation on an axis intersecting the axis of the frame, a grinding wheel car- Y ried b the shaft, and means for longitudinal a justment of the shaft along itsaxis of rotation. Y

28. A machine tool having a work holder, a tool holder adapted to present a tool to the work, and a support in which the tool holder 'is journalled, the projected axis of the tool holder in its support passing approximatelythrough the point of application of the tool tothe work whereby the tool may be reversed to present its face at a similar angle iii the opposite'direction'.

29. A machine tool having a tool post, a tool holder at an oblique angle to the axis of the work, a spindle journalled 'in the tool holder and adapted to rotate the tool, the tool holder being pivoted to the post and adapted to swing about an axis lying approximately in aV plane containing the axis of the spindle whereby the position of the tool holder relatively to the work may be reversed to thereby reverse the angle presented by the tool to the work.

i 30. 'A hob grinder having a tool ost, a tool carrier, a spindle joiirnaled in said carrier and adapted to carry the grinding wheel, and a work spindle for supporting and rotating the hob, the tool carrier hold-1 ing the axis of the tool spindle at an oblique angle to the` hob axis and the tool carrier being pivoted to the tool post upon an axis oblique to the axisof the tool spindle.

31. A relievin hob grinder having a rotatable works indie adapted to carry the h ob, a post, a rame journalled in said post `about van axis which, if extended or produced, will approximately pass through the axis of the work spindle, a grinder spindle journaled in said frame and adapted to hold theigrinder in contact with the hob at a point approximately in line with the axis of rotation of the frame, means for producing relative travel between the post and the work spindle in as direction parallel to the axis'of the work spindle, and means o erating in timed relation with the speed o rotation of 'the work spindle for periodically ef` fecting relativev movement between said frame and the work s indle in a. direction approximately dperpen icular to the axis of the work 'spin e. i

32. A machine for grinding either straight-gashed or spiral-gashed liobs hav- `iiig a spiral series ofteeth, said machine comprism in combination, means to support the ob; a grindin wheel having a perilphery shaped to grin one side at a time of t 1e spiral series of teeth; a frame 'tosupport said grinding wheel, said frame being ica pivoted to swing through 180 bo position wheel being in the axis of said lframe; and the periihely -o the wheel fer grinding means to e ect relative reciprocaton of the either si e o said spiral Series of teeth, the wheel and the hob to relieve said teeth. l0

axis of said frame being perpendicular In testimony whereof, I have hereunto 5 to the axis of the hob, the point of interseeset my hand` tion of the piteh line of the hob and the line of contact of the hob ma the grinding JOHN EDGAR.

pivoted to swing through 180 to position wheed bein in the axis of said frame; and the peri he yof the wheel for grinding means to e ect relative reciprocation of the either side oli'ysaid spiral series of teeth, the wheel and the hob to relieve said teeth. 10 axis of said frame being perpendicular In testimony whereof, I have hereunto 5 to the axis of the hob, the point of intersecset my hand tion of the pitch line of the hob and the line of contact of the hob and the grinding JOHN EDGAR.

"eminem of mman.- A It is hereby certified that the name of the assignee in Letters Patent-No.51,56

064. November 10, 1925,-up0n the apsication of John Edgar, of p HobGrin ,'ng Machines was erroneously written mois., for an im ovemen't m and rxnted as arberfColeman Company, whereas said name should have been wrlt n and printed as-Barber-Ualman Compran page 4, line 25,-for'theword-y f productxng' reed pwd-wing; and that the said tters Patent should be lead with. these corrections therein that the Vsmme 4may conform tothefrecor'd .of 'thefca in 4the Patent Olice. j' p p, L

-f iggggand'eealledthis'th day of Januar-35A. 1131926. i, e

"F producting read producing,- and than. the said It 1`s hereby certified that the name of the assignee in Letters Pamnz'lo.V 1,561,064, ted November 10, 1925, upon the glp Iication of John Edgar, of Rockford.l 'noi's, for an im rovement inl HobGrin 'ng Machines, was erroneously written ami printed as arbor-Coleman Company, whereas sand name shnuld have been written ima printed as-Barbw-Uolman Campanie;A pageP/i, line 25,-forthe" w 1rdv fiers mnt should be read with Ithese corrections therein that the same may conform to thereoorof thelcgse in' the 

